Method and apparatus for robotic launch and capture of a UAV

ABSTRACT

An apparatus and system for launching and/or capturing an unmanned aerial vehicle (UAV). The apparatus includes a moving substrate having an electromagnetic end effector and a UAV with a metallic strike plate to be attracted to the end effector when the electromagnet is activated. The system includes a movable robotic arm having a free end and a secured end; an electromagnetic end effector connected proximate to the free end of the robotic arm; a UAV with a metallic strike to be attracted and held to the electromagnetic end effector when the electromagnetic end effector is active; trajectory software configured to control a location of the free end of the robotic arm; and a control module for receiving input data, analyzing the data and using the trajectory software to control the location of and activate or deactivate the electromagnetic end effector. Also described are methods for launching and capturing the UAV.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.provisional application No. 62/538,419, filed on Jul. 28, 2017, theteachings of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

A robotic launch and capture apparatus and system for use with unmannedaerial vehicles (UAV). The apparatus utilizes an electromagneticcompliant end effector connected to a robotic arm. Also described aremethods of controlling the robotic arm to effect launch and capture.

BACKGROUND

In the past decade, Unmanned Aerial Vehicles (UAVs) have become anincreasingly crucial facet of many Department of Defense (DoD)operations, due to their versatile and reliable defensive andsurveillance capabilities. The DoD currently utilizes several differenttypes of UAVs, with many different capabilities. The smaller systems,referred to as Tier 1 UAVs, primarily perform low-altitude tasks. Tier 1UAVs range from three to five kilograms in weight. The larger systems,Tiers 2 & 3 perform high-altitude tasks and weight over ten to hundredsof kilograms. Even though all of these UAVs are extremely versatile andautonomous once they are airborne, virtually all of these aerial systemsrequire direct human involvement during launch. The lighter, Tier 1systems are usually launched by hand, while the heavier Tier 2 & 3systems are launched using large pneumatic or elastic catapults, whichoften require two or more personnel to set up and reload after eachlaunch. The UAV launch systems currently used lack two crucialcharacteristics: autonomy and repeatability.

The current state-of-the-art systems in non-runway UAV capture have twocrucial problems. The broad capture mechanism of these UAV capturesystems is a net and a snag-wire, respectively. Net capture systemstypically consist of a large rectangular surface of webbing, supportedupright by an external structure. While the net system allows UAVcapture without a runway, the deceleration of the UAV is uncontrollable,leading to stresses on the structure of the vehicle. Additionally, thegenerally massive size of the system leads to the possibility ofentanglement.

Snag-wire capture systems consist of a wire suspended by a crane. Asmall hook attached to a wing of the UAV snags the wire, causing the UAVto quickly decelerate and spiral erratically around the wire. Similar tothe net system, the snag-wire system requires multiple personnel tofunction, and can cause signification stress on the UAV. The two mainproblems with the current UAV capture systems are the lack of autonomyand lack of controlled deceleration.

Current UAV launch systems are either human powered or require on-sitehuman involvement for operation. UAV launch from a robotic arm systemwould permit UAV deployment and capture to be both autonomous andrepeatable, providing a safer, faster, and more reliable launch system.A robotic arm UAV capture system has the potential to provide bothautonomous and repeatable capture, as well as controlled deceleration tominimize UAV stress.

SUMMARY OF THE INVENTION

The present disclosure relates to an apparatus and system for launchingand/or capturing a UAV. The disclosure is also related to methods oflaunching or capturing a UAV.

One embodiment of the invention relates to an apparatus for capturing anunmanned aerial vehicle. The apparatus comprises a moving substrate, anelectromagnetic end effector connected to the moving substrate, and ametallic strike plate located on the unmanned aerial vehicle andconfigured to be attracted and securely held to the electromagnetic endeffector when the electromagnetic end effector is activated.

In the forgoing embodiment, the moving substrate is configured toprovide a desired orientation and velocity of the electromagnetic endeffector, preferably the moving substrate is a robotic arm.

In each of the forgoing embodiments the apparatus may also comprise adata collection module for collection of motion data of the unmannedaerial vehicle, a data analysis and computation module for determining afuture path of the UAV from the motion data collected by the datacollection module and constructing a trajectory path for theelectromagnetic end effector using said future path of the UAV, and acommunication module for communicating said constructed trajectory pathto the robotic arm for execution.

Another embodiment of the invention describes a system for launchingand/or capturing an unmanned aerial vehicle. The system comprises amovable robotic arm having a free end and a secured end, anelectromagnetic end effector connected proximate to the free end of therobotic arm, a metallic strike plate located on the unmanned aerialvehicle to be attracted and securely held to the electromagnetic endeffector when the electromagnetic end effector is active, trajectorysoftware configured to control a location of the free end of the roboticarm, and a control module for receiving input data, analyzing the dataand using the trajectory software to control the location of the freeend of the robotic arm and activate or deactivate the electromagneticend effector.

In each of the forgoing embodiments, the electromagnetic end effectorfurther comprises at least one aligning rail positioned and configuredfor aligning the unmanned aerial vehicle in a particular orientationrelative to the electromagnetic end effector.

The system of the above embodiment may also comprise a data collectionmodule for collection of motion data of the unmanned aerial vehicle andcommunicating said motion data to said control module. The controlmodule determines a future path of the UAV from the motion datacollected by the data collection module and constructs a trajectory pathfor the electromagnetic end effector using said future path of the UAV,and the system may also comprise a communication module forcommunicating said constructed trajectory path to the robotic arm forexecution.

Each of the forgoing embodiments may further comprise an actuatorconfigured for activating and deactivating an electromagnet of theelectromagnetic end effector. The control module is configured to causethe actuator to deactivate the electromagnet at a launch time when saidUAV has achieved a sufficient velocity and is positioned at suitablelaunch angle.

Another embodiment of the invention is a method of capturing an unmannedaerial vehicle provided with a metallic strike plate, said methodcomprising steps of: directing the unmanned aerial vehicle on a paththat intersects a work envelope of a robotic arm comprising a free endand a secured end, and an electromagnetic end effector located proximateto the free end of the robotic arm, obtaining motion data for theunmanned aerial vehicle, and controlling a location of the free end ofthe robotic arm based on the motion data to position the electromagneticend effector for interaction with the metallic strike plate of theunmanned aerial vehicle when the unmanned aerial vehicle is presentwithin the work envelope of the robotic arm to capture the unmannedaerial vehicle.

In the forgoing method, the step of controlling a location of the freeend of the robotic arm comprises a step of determining a future path ofthe UAV from the motion data, and the controlling step further comprisesa step of constructing a trajectory path for the end effector using thefuture path of the UAV.

In each of the forgoing embodiment the trajectory path is apoint-to-point trajectory path, preferably, the point-to-pointtrajectory path is a point-to-point trajectory path with a referencepoint.

In each of the forgoing embodiments, the constructed trajectory pathincludes a start time at which movement along said constructedtrajectory path is initiated.

Additional details and advantages of the disclosure will be set forth inpart in the description which follows, and/or may be learned by practiceof the disclosure. The details and advantages of the disclosure may berealized and attained by means of the elements and combinationsparticularly pointed out in the appended claims. It is to be understoodthat both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the disclosure, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a diagram of a robotic system according to an embodiment ofthe invention as used to launch a UAV.

FIG. 2 is a diagram of a robotic system according to an embodiment ofthe invention as used to capture a UAV.

FIG. 3 is a computer rendering of an embodiment of an end effector andfuselage rails according to an embodiment of the invention.

FIG. 4 is a picture of a fuselage of a UAV aligned with an end effector.

FIG. 5 is a depiction of a robotic arm used in one embodiment.

FIG. 6 is a depiction of a robotic arm showing two different types ofmotion.

FIG. 7 is a diagram of a linear trajectory path type.

FIG. 8 is a diagram of a point-to-point trajectory without a referencepoint path type.

FIG. 9 is a diagram of a point-to-point trajectory with a referencepoint path type.

FIG. 10 is a picture of a communication module according to anembodiment.

FIG. 11 is a flowchart showing the hierarchy of software communicationthat is able to perform a robotic UAV capture.

FIG. 12 is a graphic of the extrapolated UAV path, work envelope, enterpoint, exit point, and catch point.

FIG. 13 is a graphic representation of the translated path-matchingmotion

FIG. 14 is a graphic representation of a smooth end-effector catch path.

FIG. 15 is a display of oscilloscope data from the KRC for thetrajectory shown in FIG. 7.

FIG. 16 is a display of oscilloscope data from the KRC for thetrajectory shown in FIG. 8.

FIG. 17 is a display of oscilloscope data from the KRC for thetrajectory shown in FIG. 9.

FIG. 18 is a picture of an embodiment of an end effector attached to amoving substrate.

DETAILED DESCRIPTION

The present invention relates to a UAV launch and/or capture system thatcan provide autonomous launch, capture, and recharge of UAVs. The systemfor robotic launch and/or capture of UAVs utilizes an electromagneticend effector.

Also disclosed is a method of launching a UAV that can be carried outusing the UAV launch and/or capture system, as well as a data capture,processing and execution method suitable for execution of the method tocapture a UAV using the system.

In order for a UAV to be successfully launched, the launch mechanismmust ensure that the UAV attains a certain launch velocity and mustposition the UAV at a suitable launch angle at the moment of release togenerate enough lift and momentum for the onboard motor system of theUAV to successfully take over control and maintain the UAV in flight.

The general premise of the throwing mechanics of the UAV systemutilizing a robotic arm is shown in FIG. 1. In order for the robotic armto launch a UAV, the arm first accelerates the UAV to its requiredlaunch velocity and at the same time positions the UAV at a suitablelaunch angle using a programmed trajectory path. The compliant endeffector is caused to release the UAV system at the desired moment oflaunch, and the UAV is launched from the robotic arm.

Use of a robotic UAV capture system decreases the required space, set uptime, human interaction, and physical stress on a UAV during capture.The general premise of the capture mechanics of a UAV system utilizing arobotic arm is shown in FIG. 2. In order to perform successful UAVcapture, the capture system requires data collection and analysis and acommunication module to cause execution of commands based on theanalyzed data. The capture system must be able to obtain raw datarepresentative of the motion of the UAV to be captured. Software, suchas the MATLAB script used in one embodiment of the invention, is able toprocess the raw motion data to extrapolate a flight path of the UAV, andcalculate a smooth Cartesian end-effector catch path, which can be usedto manipulate the robotic arm to cause motion of the end effector tomatch the desired catch path with proper timing and orientation forcapture of the UAV.

UAV Launch and Capture System

The robotic launch and/or capture apparatus 100 shown in FIGS. 1 and 2utilizes a moving substrate 102 shown as the preferable robotic arm andan end effector 104 attached proximate to a free end of robotic arm 102to launch and/or capture a UAV 106. To launch a UAV using the apparatusof FIG. 1, a strike plate 108, which is configured for interaction withend effector 104 is attached to, or forms a part of UAV 106. Usingstrike plate 108, UAV 106 is secured to end effector 104 that, in turn,is affixed to robotic arm 102 of robotic launch and/or capture system100. To launch UAV 106, trajectory software of a control module causesrobotic arm 102 to move in a manner which accelerates UAV 106 to adesired launch velocity and positions UAV 106 at a suitable launchangle. When UAV 106 reaches launch velocity and is positioned at asuitable launch angle, the control module communicates with end effector104 to cause end effector 104 to release UAV 106 thereby launching UAV106.

To capture UAV 106 using the launch and/or capture system as shown inFIG. 2, raw motion data of an incoming UAV 106 is collected by thesystem. The motion data is analyzed using software of the control moduleto construct a smooth catch path for end effector 104. The controlmodule then controls robotic arm 102 to position end effector 104 andcause end effector 104 to follow the constructed catch path at theappropriate time. The control module also activates the end effector atthe correct time during capture to attract the UAV. Preferably, when endeffector 104 is initially positioned proximate to the beginning of theconstructed catch path, an electromagnet on end effector 104 is activefor attracting and securing UAV 106 to end effector 104, therebyresulting in capture of UAV 106.

The end effector 104 is a mechanism positioned proximate to the free endof robotic arm 102. End effector 104 includes suitable apparatus forinfluencing its surrounding environment, for example, an electromagnetfor creating a magnetic field in the environment surrounding endeffector 104. End effector 104 may also include any other mechanicalmechanism that is capable of securely holding the UAV and releasing theUAV at the desired launch angle and speed for launch, and is alsocapable of securing the UAV upon capture. The end effector has threedesign characteristics, it is stable, non-intrusive, and preferablybi-directional, meaning it can be used for both launching the UAV andfor recovering the UAV.

In some embodiments, the system for capturing and/or launching a UAVincludes a tool, or end effector 104 that is mountable to a flange ofrobotic arm 102. End effector 104 is capable of holding and releasingUAV 106 on command, and is preferably an electromagnetic end effector.The system may include an actuator configured for activating anddeactivating the end effector, preferably the electromagnet of theelectromagnetic end effector. The control module causes the actuator todeactivate the electromagnet at a launch time when said UAV has achieveda sufficient velocity and is positioned at suitable launch angle.

In one embodiment for use with Tier 1 UAVs, the end effector 104 isunder the payload limit of about 3 kg, and lightweight robots (LWR) areused. LWR have a payload limit of 7 kg. The weight limit for endeffector 104 is reduced to account for the additional weight of UAV 106so that it can be located on robotic arm 102 during deployment. Otherrobotic arms having higher payloads can be used in this system. With theuse of such robotic arms, larger UAVs, and an increase in the weight ofthe end effector 104 can be tolerated.

A preferable end effector design utilizes an electromagnet to achievethe three characteristics of the end effector, namely, stable,non-intrusive, and bi-directional. In one embodiment wherein a Tier 1UAV is being utilized, a 1.5″ 6V electromagnet may be used as part ofthe end effector. The end effector also preferably comprises analignment device used to maintain the alignment of the UAV in a singledirection during launch and recovery. Preferably, this alignment deviceincludes two aligned fuselage rails.

FIG. 3 shows an embodiment of a mechanical design for the end effector104, and FIG. 18 is a picture of an end effector comprising anelectromagnet 112 attached to a robotic arm according to an embodimentof the invention. In this embodiment, the end effector 104 is configuredfor use with a KUKA LWR 4+ robotic arm and a Tier 1 UAV. The endeffector 104 securely anchors an electromagnet to the flange of the LWRusing four M6 mount screws. The 1.5″ (not shown) electromagnet isfastened into the end effector 104 using a 10×32 bolt threaded into thebody of the end effector. Two aligning fuselage rails 110 serve toensure UAV alignment during deployment. Each of the two curved rails arescrewed into a slot located on each side of the electromagnet, in orderto allow the fuselage of the UAV to align itself with the end effector104 such that the front of the UAV is facing the same directionthroughout the entire deployment. As shown in FIG. 4, although anyalignment device may be used for this purpose, the use of two removablealigning fuselage rails adds a level of adjustability to the system,which allows different types of UAV systems to be deployed with oneconfiguration of end effector 104 by changing either the location offuselage rails, or exchanging the fuselage rail units for different sizealignment units.

Since most UAV systems have fuselages constructed of fiberglass orcarbon fiber, direct contact between an electromagnet and the body ofthe UAV will not provide a sturdy connection. To solve this problem, ametallic strike plate is attached to the UAV, preferably on a bottomsurface thereof, in order to provide a magnetic surface for theelectromagnet to interact with. The metallic strike plate is configuredto be attracted and securely held to the electromagnet end effector whenthe electromagnet is activated. In the preferred embodiment discussedabove, a 1.5″×2.5″ steel strike plate is attached to the bottom of theUAV. The addition of a strike plate is not necessary if the UAV itselfis made from a metallic material or comprises a sufficiently largeportion of metallic material to provide a minimum level of interactionwith the electromagnet of the end effector.

Moving Substrate

Any device that can be configured to move in a specified direction canbe used as the moving substrate. The moving substrate is configured toprovide a desired orientation and velocity of the electromagnetic endeffector. Preferably, the moving substrate is a robotic arm, but couldinclude other movable items, such as a car, ship, truck, train, airplaneor another UAV. When a robotic arm is used, any robotic arm that iscapable of being programmed to move in a specific direction and speed,and hold at least the weight of the UAV can be used in the presentapparatus and system. In one embodiment the KUKA Lightweight Robot (LWR)4+ shown in FIG. 5 is employed. Larger robotic arms, such as the KR 20-3can also be used with their corresponding robotic control systems andprogramming language to perform similar movements as described herein.The LWR is a 7-degree-of freedom robotic arm capable of manipulating apayload of up to 7 kg (15.4 lbs.). Each of the joints on the LWR arecontrolled using a communication module, which in this case is the KUKARobot Control (KRC) teach pendent, which is a custom Windows®-basedsoftware interface that is capable of accurately adjusting each jointwith a ±0.1 mm accuracy. The KRC uses a programming language called KUKARobot Language (KRL) to send motion and information commands to and fromthe LWR. The throw trajectory software for the present system may beprogrammed in KRL for use by the KRC.

Three specific types of commands are used for the trajectory software:motion commands, data retrieval commands, and serial communicationcommands. Motion control allows the KUKA robotic arm to move relative toits surroundings. The LWR moves using three types of movements: PTP(Point to point movement), LIN (Linear movement), and CIRC (Circularmovement). In the programming in the preferred embodiment of the presentsystem, two motion commands employing PTP and LIN motion account for themajority of the motion of the robotic arm. Both PTP and LIN motion havetheir positives and negatives, all of which were considered whenprogramming the throw trajectories for the present system.

PTP motion has a high path speed and low path accuracy, whereas LINmotion has a low path speed and high path accuracy. In FIG. 6, a visualcomparison between PTP and LIN motion can be seen. The green PTP motionshows a fast, albeit curved motion between two points, while the red LINmotion shows a slower, yet perfectly straight motion between two points.The throw trajectories developed using KRL for one embodiment of thepresent system are described in more detail below use LIN and PTPmotion.

Another KRL feature used in the described embodiment of the presentsystem was data retrieval. While the LWR performs certain KRL motioncommands, a multitude of variables are calculated, each pertaining todifferent mechanical and electrical characteristics of the robotic armat any point in time. The two KRL variables that were stored duringthrow trajectory testing are displayed in Table 1.

TABLE 1 Variable Abbreviated Name Description Variable Name $POS_ACT.CValue of the angle of elevation C of the end effector, in degrees$VEL_ACT Value of the angle of elevation V of the end effector, indegrees

Within the KRL software, the C and V variables represent the endeffector's angle of elevation and velocity, respectively. Both of thesevariables are recorded during the throw trajectory using an oscilloscopeprovided within the KRC, and the C and V values recorded throughout theduration of each trajectory motion are stored.

The third KRL command utilized for the interface is serialcommunication. A communication module preferably uses the third KRLcommand for communication of the constructed trajectory path to therobotic arm for execution. In order for the LWR to communicate with theend effector, a command is outputted by the KRC, and the end effectorresponds accordingly. The KRL commands CWRITE and CREAD were used tocommunicate between the LWR and an Arduino microprocessor to control theend effector in the described embodiment.

UAV Launch

The task of successfully deploying a UAV from the robotic arm requiresthat the compliant end effector and the robotic arm work in unison toensure that the UAV is released at a desired launch velocity andsuitable launch angle. As such, there are three components of aneffective UAV-deploying system: 1.) the compliant robotic end effector,2.) the control module for using the trajectory software for the roboticcontroller, and 3.) a communication module as an interface between theend effector and the trajectory software used by the control module.

The compliant robotic end effector includes a mechanical and electricalsystem capable of quickly capturing and releasing the UAV on command toensure that the UAV is reliably released at the moment of launch, asdiscussed in detail above. Preferably, the end effector is a magneticgrip end effector. The trajectory software for the robotic controller isconfigured to ensure that the robotic arm moves in a desired constructedpath at a certain speed to ensure that the UAV system is launched at therequired launch velocity and a suitable launch angle at the moment oflaunch. The interface between the end effector and the trajectorysoftware of the control module is adapted to ensure that the endeffector and the trajectory software quickly and accurately communicateto ensure proper timing for the acceleration, positioning and release ofthe UAV during launch.

Trajectory Software

The trajectory software can be developed using the control module andprogramming language for the specific moving substrate, preferably arobotic arm that is utilized in the system. The primary objective is tocreate a program capable of accelerating the end effector and UAV on theLWR to a required velocity and at the same time position the UAV at asuitable launch angle for deployment. In one embodiment, the two KRLmotion commands that were used within the throw trajectory programs werePoint-to-Point (PTP) and Linear (LIN) motion commands. Although any pathtype resulting in a suitable launch angle and launch velocity for theUAV can be used, in one embodiment, three different trajectory pathtypes were programmed on the KRC. Each trajectory path type utilizeddifferent aspects of PTP or LIN motion. Each trajectory path type isdescribed with a diagram shown in the figures. The red vectors representthe orientation of the UAV at each point.

1: Linear Trajectory is shown in FIG. 7—This trajectory utilizes alinear motion from a start point (P_S) to an end point (P_E). Theorientation of the end effector is programmed to stay constant, thus theangle of elevation is also kept constant. The path length is short dueto restrictions in the work envelope of the LWR.

2: PTP Trajectory (No Reference Point) is shown in FIG. 8—Thistrajectory utilizes a point-to-point motion from a start point (P_S) toan end point (P_E). The orientation of the end effector is programmed tochange during the motion. Thus, the angle of elevation also changesduring the motion. The path length is longer than the linear motion ofFIG. 7 because this path is curved.

3: PTP Trajectory (With Reference Point) is shown in FIG. 9—Thistrajectory utilizes a point-to-point motion from a start point (P_S), toa middle reference point (P_R), and then to an end point (P_E). Theorientation of the end effector is kept constant between the start pointand the reference point. The path length is also long because it iscurved.

A control module uses the trajectory software to determine the futurepath of the UAV, and can utilize any of the trajectory paths describedabove, or a different path that utilizes different known commands tocontrol the motion of the moving substrate. The constructed trajectorypath includes a start time at which movement along the constructedtrajectory path is initiated.

Release Timing Interface

In the preferred embodiment, for the end effector to respond quickly andefficiently to commands sent through the trajectory software of therobotic arm, a robotic arm controller termed the “Release TimingInterface (RTI)” was designed for providing communication between thetrajectory software and the end effector. One objective of the RTI wasto provide an electronic system capable of interpreting serial commandsof the robotic arm controller to control an actuator used to activate ordeactivate the electromagnet of the end effector. The serial commandsmay be obtained from a control module of a robotic arm, or a dataanalysis and computation module. Since interpreting serial commands fromthe KRC requires computation, an Arduino microprocessor board was usedalong with a serial port shield to interpret the serial signal. The 1.5″electromagnet used on the magnetic grip end effector required 6 voltswith 1 amp of current to activate properly. The Arduino microprocessorcould only output 5V at 40 mA, so an external relay acting as a switchwas used to allow the Arduino microprocessor to open and close anexternal circuit for the electromagnet.

Each component of the RTI is shown in FIG. 10. The Arduinomicroprocessor could only take serial commands from a computer, but notthe actual KRC, which resulted in significant limitations for theapplication of this system within the KRL and KRC environment.

Software for Robotic Capture

The three main features of a successful robotic capture are datacollection, data analysis, and data execution. The process of catching aUAV by means of a moving substrate, preferably a robotic arm, would beimpossible without compliance obtained by using live data on thekinematic behavior of the incoming UAV. Data collection refers to theway that kinematic motion data is gathered and is accomplished by a datacollection module. Data analysis refers to the computation andprocessing performed on the collected data in order to construct aneffective catch path for the end-effector, which is performed by a dataanalysis and computation module, or a control module. Data executionrefers to the way in which this catch path is communicated to andexecuted by the robotic arm, and is performed by a communication module.A fully functioning robotic arm UAV capture system requires real-timecommunication between each of these components. In some embodiments, themotion is determined recursively. There are many combinations ofhardware and software capable of handling the processing load and basicfunctions required to execute these three features of a robotic UAVcapture. FIG. 11 shows an exemplary hierarchy of software communicationthat can be used to perform a robotic UAV capture, using suitable codingand hardware. The two programs that were used in the embodimentdescribed herein are Motive and MATLAB.

The data collection module must be capable of tracking and communicatinglocation data of an incoming UAV. Any motion capture system would becapable of this task. Suitable motion capture systems are typicallyfound in the production industry, and are composed of multiple types ofcameras and software. These systems are capable of accurately trackingand recording the motion of tracking points. The motion capture systemused in the embodiment discussed herein was the OptiTrack Trio, whichemploys a three camera setup, which tracks and records motion data usinga program called Motive. The OptiTrack Trio is capable of tracking thelocation of a tracking point to within a fraction of a millimeter at arate of 120 Hz.

The data analysis and computation module, or in some embodiments thecontrol module requires a program capable of performing mathematicalcalculations. While virtually any computer language might be capable ofperforming the calculations, a mathematics program called MATLABprovides good graphical feedback. A MATLAB script was used to performpost-processed data analysis. The communications module can be a RobotOperating System (ROS) used for data execution, upon communication ofthe path constructed using the MATLAB program to the ROS.

I: Data Collection

1.1: Motive software

Tracking the motion of the UAV is completed by a data collection module.In an embodiment the data collection module may be a motion capturesystem called the OptiTrack Trio, using the motion capture programMotive. The OptiTrack Trio is accurate to within three tenths of amillimeter. OptiTrack camera systems are commonly used in the field ofvideo special effects. The OptiTrack Trio is able to track any infraredreflective material. Spherical reflective tracking dots are often usedin scenarios where the orientation of the object being tracked changessignificantly.

1.2: Method of Data Collection

A reflective sphere may be placed on the midsection of the UAV'sfuselage. For testing purposes, six trials of gliding flight werecollected. The UAV is thrown in the general direction of the Trio. Ofthe six trials, the first three served as guidance for the algorithmdevelopment and the remaining three provided test data for the finalMATLAB script. The data is recorded on Motive and then exported as a CSV(comma-separated-variable) file. CSV files are easily read byprogramming platforms, including MATLAB.

2: Data Analysis

TABLE 2 Description MATLAB Function Name polyfit(data1, data2, n)Polynomial regression of data1 vs. data2 to the n^(th) degreecsvread(filename, a, b) Reads data from CSV file, filename, with rowoffset (a, b) csvwrite(filename, M) Writes a CSV file, filename, fromdata in matrix M fzero(f, g) Finds zeros of function f with the startingguess g plot(data1, data2) Plots data1 vs. data 2 saveas(f, filename,filetype) Saves figure f with a filename filename with a file typefiletype Variable Name cartDat Raw (x, y, z) data read from the CSV filerotCartDat Rotated (x, y, z) data pEnter = (tEnter, xEnter, zEnter) Timeand location glider enters work envelope of arm pOver = (tOver, xOver,zOver) Time and location glider is first directly above arm pCatch =(tCatch, xCatch, zCatch) Time and location arm catches glider pExit =(tExit, xExit, zExit) Time and location glider exits work envelope ofarm catchRatio Ratio of the time difference for calculating catch pointplaneStartPos Arbitrary start position for the glider armStartPos =(tOver, xArmStart, Arbitrary start position for the zArmStart) arm's endeffector finalArmDat Final time and location matrix of end-effector path2.1: Cartesian Rotation

Once the motion data is obtained, the data analysis and computationmodule is used to determine the future path of the UAV from the motiondata collected by the data collection module. From the analysis themodule constructs a trajectory path for the electromagnetic endeffector, and can include a start time at which movement of along saidconstructed trajectory path is initiated. In some embodiments the sameanalysis may be performed by a control module. The first step inprocessing the CSV file from Motive is to perform initial processing toproject the 3-D Cartesian data (x,y,z) onto the 2-D x-z plane throughthe use of a 3-D rotation matrix. Raw Cartesian data was read by MATLABfrom each CSV file and used to populate a three column matrix calledcartDat. The heading of a flight-path is defined by the angle betweenthe x-y direction of motion and the positive x-axis. Finding the headingof the raw data stored in cartDat involves multiple steps. First, theraw data is translated by the negative of the initial position value inthe matrix. This translates the dataset to begin at the origin. Theheading angle, θ, is then calculated by taking the inverse tangent ofthe slope of a linear regression on the x-y plane. The cartDat matrix isrotated θ degrees counterclockwise around the z-axis by a 3-D rotationmatrix, and then populates a new matrix cartDatRot:

$\lbrack{cartDatRot}\rbrack = {\begin{bmatrix}x_{0} & y_{0} & z_{0} \\\bullet & \bullet & \bullet \\\bullet & \bullet & \bullet \\x_{f} & y_{f} & z_{f}\end{bmatrix} \star \begin{bmatrix}{\cos(\theta)} & {- {\sin(\theta)}} & 0 \\{\sin(\theta)} & {\cos(\theta)} & 0 \\0 & 0 & 1\end{bmatrix}}$

The original row of timestamp values is then concatenated ontocartDatRot. After rotation, the y-values of cartDatRot are negligible,so the y-value row is removed. The cartDatRot matrix gives the behaviorof the x and z values of the UAV vs. time.

2.2: Parametric Extrapolation

The second step in analyzing the motion data is to extrapolate theposition of the UAV at future timestamps. Due to the fact that theflight path of a UAV is a linear descent, the motion of the UAV isextrapolated by two linear parametric equations, x(t) and z(t). Theseequations are calculated by performing a polynomial fit between thetime-column and xyz-column of cartDatRot. Given these parametricequations, the x-z location of the UAV vs. time can be calculated. Theextrapolated data populates a matrix, and translates to start at thepoint planeStartPos.

2.3: Critical Points Determination

A robotic arm's work envelope is the area in which the arm is able toeffectively reach and manipulate. A generalized work envelope of arobotic arm is modeled by a semicircle, radius R, with a center at theorigin. Given the equation of the outer edge of the work envelope andthe two parametric equations calculated in 2.2, the location and time atwhich the UAV enters and exits the work envelope are determined with thefzero function. These values are (tEnter, xEnter, zEnter) and (tExit,xExit, zExit). The point of catch is calculated by finding a timestampvalue tCatch that is a certain ratio, catchRatio, between tEnter andtExit, given by:tCatch=tEnte7′+(catch Ratio*(tExit−tEnter))

Given tCatch, xCatch and zCatch are then calculated by plugging tCatchinto the parametric equations from 2.2. A diagram of the extrapolatedUAV path, work envelope, enter point, exit point, and catch point aredisplayed in FIG. 12.

2.4: Translated Path-Matching

After the point and time of catch is calculated, a smooth catch motionpath for the end effector of the robotic arm must be determined. Thispath must smoothly approach the catch point determined in 2.3 and reachthe catch point at the timestamp tCatch. An arbitrary start point forthe end effector is given by a coordinate within the work envelope,armStartPos. The path planning algorithm constructs this smooth motionpath in two parts: translated path-matching and offset-correction, whichprovides horizontal and vertical motion planning, respectively. Eachpart constructs two parametric paths, which are added at the end toproduce a desired smooth curve. Translated path-matching directly copiesthe extrapolated UAV motion and translates it to begin at the startpoint for the arm. The time and location at which the UAV crosses thestart position for the arm is given by (tOver, xOver, zOver). Thetimestamp column of the translated motion data is shifted by tOver toaccurately represent the arm's position relative to the plane. A graphicof the translated path-matching motion is shown in FIG. 13.

2.5: Offset-Correction

If the translated path-matching motion calculated in 2.4 was executed byitself, the displacement between the UAV and the arm would remainconstant. Therefore, in order to catch the UAV, this displacementbetween the UAV and the arm must be decreased to zero between thetimestamps tOver and tCatch. Given that the translated path-matchingmotion from 2.4 is linear, and the end goal is a smooth parametric path,the offset-correction must be decreased smoothly. The goal of the offsetcorrection function is to decrease the initial displacement, given by(zOver−zArmStart), smoothly to zero between the timestamps tOver andtCatch. The parametric function zCurve defines a parabola with at-intercept of (t,z)=(tOver, 0), and a maximum at (tCatch,(zOver,zArmStart)). zCurve is given by the equation:

${zCurve} = {- {\left\lbrack {{zOver} - {zArmStart}} \right\rbrack\left\lbrack {\frac{\left( {t - {tCatch}} \right)^{2}}{\left( {{tOver} - {tCatch}} \right)^{2}} - 1} \right\rbrack}}$

Given the translated path-matching motion defined in 2.4 and theoffset-correction motion defined by zCurve in 2.5, the desired smoothcatch curve can be calculated by adding these two paths. By adding thepath-match and zCurve, a path is created that starts at armStartPos andsmoothly approaches the catch point, and finally reaches the catch pointat the proper catch time.

3: Data Execution

3.1: Arm Reference Frame

-   Given the smooth path constructed at the end of 2.5, a three column    matrix, finalArmDat, is populated, which gives the desired location    vs. time data for the end effector. The coordinates along the path    given by finalArmDat are, in respect to the origin, defined by the    center of the arm's work envelope. This means that the motion data    is in respect to the arm's reference frame, which is required for a    robotic arm path.    3.2: CSV Export

The data in finalArmDat is written into a new CSV file through thefunction csvwrite. The CSV file includes timestamps that correspond withend-effector coordinates. CSV files can be read by robot controlsoftware such as a Robot Operating System (ROS), which can act as thecommunication module to effectuate the movement of the robot arm.

Results

For data collection, the OptiTrack Trio camera system effectively andaccurately recorded the position and motion of the UAV, and can outputCSV files that are readable by MATLAB. For data analysis, the MATLABscript executes the five algorithm steps: Cartesian-rotation, parametricextrapolation, critical points determination, translated path-matching,and offset-correction. When working in unison, each step of the pathplanning script is able to calculate a smooth end-effector catch path asshown in FIG. 14. The MATLAB script was able to successfully performsimulated catches for the first three trials of CSV motion data, as wellas the last three unique trials. Testing the path planning script withthe last three files demonstrated the algorithm's level of usabilitywith raw data. Overall, the path planning algorithm proved to besuccessful in constructing and exporting a smooth end-effector catchpath by post-processing raw motion data of motion of a UAV.

Adapting the software discussed above to run in real-time required theuse of the other programs in FIG. 11: NAT.NET SDK for live Motive toMATLAB communication and Robot System Toolbox/Robot Operating System forMATLAB to robot communication.

Although the above robotic launch and/or capture system is described asa single system, it is understood that the launch system can be aseparate system from the capture system, and that each system can beused individually to either launch or capture a UAV. Further any elementof the system that has been described individually can also be used in acombined launch and/or capture system.

The robotic launch and/or capture system described herein can be used ina method of launching an UAV provided with a metallic strike plate. TheUAV is secured on the electromagnetic end effector by activating theelectromagnet to create an electromagnetic field. Data is input to acontrol module of the system regarding the launch velocity and angleneeded for the UAV to successfully launch. The control module andtrajectory software are used to calculate a trajectory path for theelectromagnetic end effector, as described in the trajectory softwaresection above, and the Example herein. The control module communicatesthe desired location of the free end of the robotic arm based on thetrajectory path through the use of a communication module, and theelectromagnet of the electromagnetic end effector is deactivated tolaunch the UAV when the UAV has reached the desired velocity and anglefor launch. The trajectory path can be a determined point-to-pointtrajectory path, and the point-to-point trajectory path may use areference point. A start time for the movement of the arm at which timemovement of said end effector along said constructed trajectory path isinitiated may also be controlled by the control module.

The robotic launch and/or capture system described herein can also beused in a method of capturing an UAV provided with a metallic strikeplate. The UAV is directed on a path that intersects a work envelope ofa robotic arm comprising a free end and a secured end, and anelectromagnetic end effector located proximate to the free end of therobotic arm. Motion data for the UAV is obtained and the location of thefree end of the robotic arm is controlled based on the motion data toposition the electromagnetic end effector for interaction with themetallic strike plate of the UAV when the UAV is present within the workenvelope of the robotic arm to capture the UAV.

The location of the free end of the robotic arm for controlling itsposition is accomplished by determining a future path of the UAV fromthe motion data and constructing a trajectory path for the end effectorusing the future path of the UAV. The trajectory path can be determinedby using the data analysis and computation discussed above in Section 2.Such a trajectory path can be a point-to-point trajectory path, and thepoint-to-point trajectory path may have a reference point. A start timefor the movement of the arm at which movement of said end effector alongsaid constructed trajectory path is initiated may also be determinedbased on the obtained motion data.

EXAMPLES Example 1

To analyze the kinematic characteristics of each throw trajectory planas described above, a KRC oscilloscope was used to collect data. The twovariables C and V were recorded using the oscilloscope throughout theduration of each program. C and V state the angle of elevation of theUAV and the velocity of the UAV, respectively. The three programs thatwere analyzed were the three programed trajectory paths: Linear, PTP (noreference point), and PTP (with reference point). Each trajectory wasrun at full speed, with the magnetic grip end effector and a UAVattached thereto using a metallic strike plate.

FIGS. 15, 16 and 17 display the oscilloscope data from the KRC for eachof the three trajectory programs. The yellow line on each of the graphsrepresents the V value for the end effector, or the velocity vs. time.The brown line represents the C value for the end effector, or the angleof elevation vs. time. The launch time interval for each respectivegraph is the following: Linear (FIG. 15), 1.5-3.0 sec; PTP w/o ReferencePoint (FIG. 16), 0-2.0 sec; PTP w/Reference Point (FIG. 17), 0-3.0 sec.

Certain trend types are evident across all three of the oscilloscopegraphs. Based on the objective of the throw trajectory software, havinga period of time that has a high velocity, a constant C value, and aconstant V value is desired. The terms “velocity plateau” and “Cplateau” represent periods of motion where either velocity is constantor C is constant during the launch time interval. Having a period ofconstant velocity or constant C is desired during a trajectory motionbecause it allows the UAV to be released with a more accurate launchangle and velocity. Table 3 below states the maximum velocity for eachtrajectory path type, as well as the existence of a velocity plateau orC plateau for each motion.

TABLE 3 Trajectory Maximum Velocity Plateau C Plateau Path Type Velocity(Y/N) (Y/N) Linear 0.675 m/s  N Y PTP w/o Ref. 1.0 m/s Y N PTP w/Ref.1.0 m/s Y Y

The electromagnetic end effector proved to be an effective apparatus forstrongly holding and instantaneously and reliably releasing the UAV.Once a signal was sent to the electromagnetic end effector, theelectromagnet instantly turned off, and the holding force between theend effector and the UAV was removed. When running the electromagneticend effector at 9V, a small amount of residual electromagnetic forceexisted between the end effector and the strike plate on the UAV. Whenrunning the end effector at 6V, no significant residual electromagneticforce existed after the electromagnet was turned off. The fuselage railswere effective for aligning the body of the UAV during the placement ofthe UAV on the end effector and during launch.

Certain kinematic characteristics for each of the three trajectoryprograms were collected. Table 3 shows these kinematic characteristicsfor each of the three trajectories. Of the three paths, both PTP pathshad larger overall velocities than the Linear path. Both PTP paths hadperiods of constant velocity. The Linear path and the PTP w/Ref path hadperiods of constant angle of elevation. Based on the collected data, thePTP w/Ref path reaches a max speed of 1 m/s, and has periods of bothconstant velocity and constant angle of elevation during its launch timeinterval.

The electromagnetic end effector system consisted of three parts: Theelectromagnetic end effector apparatus, the trajectory software, and theRTI. Based on the performance of the end effector apparatus, it can beconcluded that an electromagnetic end effector is a viable option forrobotic arm UAV launch. The analysis pertaining to the KRC throwtrajectory paths leads to the conclusion that the PTP w/Reference Pointis the most optimal trajectory path, because it reaches the highestvelocity of 1 m/s and has periods of constant velocity and angle ofelevation.

At numerous places throughout this specification, reference has beenmade to a number of U.S. Patents and other documents. All such citeddocuments are expressly incorporated in full into this disclosure as iffully set forth herein.

Other embodiments of the present disclosure will be apparent to thoseskilled in the art from consideration of the specification and practiceof the embodiments disclosed herein. As used throughout thespecification and claims, “a” and/or “an” may refer to one or more thanone. Unless otherwise indicated, all numbers expressing properties usedin the specification and claims are to be understood as being modifiedin all instances by the term “about,” whether or not the term “about” ispresent. Accordingly, unless indicated to the contrary, the numericalparameters set forth in the specification and claims are approximationsthat may vary depending upon the desired properties sought to beobtained by the present disclosure. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques. Notwithstanding that thenumerical ranges and parameters setting forth the broad scope of thedisclosure are approximations, the numerical values set forth in thespecific examples are reported as precisely as possible. Any numericalvalue, however, inherently contains certain errors necessarily resultingfrom the standard deviation found in their respective testingmeasurements. It is intended that the specification and examples beconsidered as exemplary only, with a true scope and spirit of thedisclosure being indicated by the following claims.

The foregoing embodiments are susceptible to considerable variation inpractice. Accordingly, the embodiments are not intended to be limited tothe specific exemplifications set forth herein above. Rather, theforegoing embodiments are within the spirit and scope of the appendedclaims, including the equivalents thereof available as a matter of law.

The applicant does not intend to dedicate any disclosed embodiments tothe public, and to the extent any disclosed modifications or alterationsmay not literally fall within the scope of the claims, they areconsidered to be part hereof under the doctrine of equivalents.

What is claimed is:
 1. An apparatus for capturing an unmanned aerialvehicle comprising: a moving substrate; an electromagnetic end effectorconnected to the moving substrate; a metallic strike plate located onthe unmanned aerial vehicle and configured to be attracted and securelyheld to the electromagnetic end effector when the electromagnetic endeffector is activated; a data collection module for collection of motiondata of the unmanned aerial vehicle; a data analysis and computationmodule for determining a future path of the UAV from the motion datacollected by the data collection module and constructing a trajectorypath for the electromagnetic end effector using said future path of theUAV; and a communication module for communicating said constructedtrajectory path to the robotic arm for execution, wherein the dataanalysis and computation module constructs a point-to-point trajectorypath.
 2. The apparatus of claim 1, wherein the moving substrate isconfigured to provide a desired orientation and velocity of theelectromagnetic end effector.
 3. The apparatus of claim 1, wherein themoving substrate is a robotic arm.
 4. The apparatus of claim 1, whereinthe point-to-point trajectory path is a point-to-point trajectory pathwith a reference point.
 5. The apparatus of claim 1, wherein theconstructed trajectory path includes a start time at which movementalong said constructed trajectory path is initiated.
 6. A system forlaunching and/or capturing an unmanned aerial vehicle comprising: amovable robotic arm having a free end and a secured end; anelectromagnetic end effector connected proximate to the free end of therobotic arm; a metallic strike plate located on the unmanned aerialvehicle to be attracted and securely held to the electromagnetic endeffector when the electromagnetic end effector is active; trajectorysoftware configured to control a location of the free end of the roboticarm; and a control module for receiving input data, analyzing the dataand using the trajectory software to control the location of the freeend of the robotic arm and activate or deactivate the electromagneticend effector, wherein the electromagnetic end effector further comprisesat least one aligning rail positioned and configured for aligning theunmanned aerial vehicle in a particular orientation relative to theelectromagnetic end effector.
 7. The system of claim 6, furthercomprising: a data collection module for collection of motion data ofthe unmanned aerial vehicle and communicating said motion data to saidcontrol module.
 8. The system of claim 7, wherein the control moduledetermines a future path of the UAV from the motion data collected bythe data collection module and constructs a trajectory path for theelectromagnetic end effector using said future path of the UAV, and acommunication module for communicating said constructed trajectory pathto the robotic arm for execution.
 9. The system of claim 8, wherein thecontrol module constructs a point-to-point trajectory path.
 10. Thesystem of claim 9, wherein the point-to-point trajectory path is apoint-to-point trajectory path with a reference point.
 11. The system ofclaim 8, wherein the constructed trajectory path includes a start timeat which movement of said end effector along said constructed trajectorypath is initiated.
 12. The system of claim 6 further comprising anactuator configured for activating and deactivating an electromagnet ofthe electromagnetic end effector and wherein the control module isconfigured to cause the actuator to deactivate the electromagnet at alaunch time when said UAV has achieved a sufficient velocity and ispositioned at suitable launch angle.
 13. A method of capturing anunmanned aerial vehicle provided with a metallic strike plate, saidmethod comprising steps of: a. directing the unmanned aerial vehicle ona path that intersects a work envelope of a robotic arm comprising afree end and a secured end, and an electromagnetic end effector locatedproximate to the free end of the robotic arm, b. obtaining motion datafor the unmanned aerial vehicle, and c. controlling a location of thefree end of the robotic arm based on the motion data to position theelectromagnetic end effector for interaction with the metallic strikeplate of the unmanned aerial vehicle when the unmanned aerial vehicle ispresent within the work envelope of the robotic arm to capture theunmanned aerial vehicle, wherein said step of controlling a location ofthe free end of the robotic arm comprises a step of determining a futurepath of the UAV from the motion data, wherein said step of controlling alocation of the free end of the robotic arm comprises a step ofconstructing a trajectory path for the end effector using the futurepath of the UAV, wherein the trajectory path is a point-to-pointtrajectory path.
 14. The method of claim 1, wherein the point-to-pointtrajectory path is a point-to-point trajectory path with a referencepoint and the constructed trajectory path includes a start time at whichmovement of said end effector along said constructed trajectory path isinitiated.